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Search: id:A144551
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| A144551 |
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a(n)=nonprimes(n)*nonprimes(n+1)/2, where nonprime(n)=A141468(n). |
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+0
1
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| 0, 2, 12, 24, 36, 45, 60, 84, 105, 120, 144, 180, 210, 231, 264, 300, 325, 351, 378, 420, 480, 528, 561, 595, 630, 684, 741, 780, 840, 924, 990, 1035, 1104, 1176, 1225, 1275, 1326, 1404, 1485, 1540, 1596, 1653, 1740, 1860, 1953, 2016, 2080, 2145, 2244, 2346
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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If n=1, then 0*1/2=0=a(1). If n=2, then 1*4/2=2=a(2). If n=3, then 4*6/2=12=a(3), etc.
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MAPLE
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A141468 := proc(n) option remember ; local a; if n = 1 then 0; else for a from procname(n-1)+1 do if not isprime(a) then RETURN(a) ; fi; od: fi; end: A144551 := proc(n) A141468(n)*A141468(n+1)/2 ; end: for n from 1 to 200 do printf("%d, ", A144551(n)) ; od: [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 03 2009]
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CROSSREFS
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Cf. A141468.
Sequence in context: A112718 A117301 A141079 this_sequence A110821 A100786 A141586
Adjacent sequences: A144548 A144549 A144550 this_sequence A144552 A144553 A144554
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KEYWORD
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nonn
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AUTHOR
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Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Dec 31 2008
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EXTENSIONS
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1963 replaced by 1953 by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 03 2009
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